Sunday, July 22, 2012

Do small men think like big women?

Endless research has been conducted on the neurological differences between women and men. However, a study out of the University of Florida explains that almost all of the anatomical differences previously reported can be accounted for simply by adjusting for total brain size.

(Lady Gaga is an excellent source of exaggerated imagery)
Leonard et al., (2008) recruited 100 men and 100 women and imaged their brains. They showed that men generally have larger brains that women (not surprising, men generally have larger bodies than women).

Leonard et al., 2008 Figure 2

But what is fascinating is that when comparing specific regions, the gender of the brain mattered less than the size of the whole brain. 

In other words if you had a small male brain, it would look almost indistinguishable from a large female brain.  (See their Figure 3)

What I find most interesting in this paper is that it refutes the much purported "Corpus Callosum Myth".

Corpus Callosum (source)
The Corpus Callosum is main white matter connection between the two hemispheres of the brain. The "Corpus Callosum Myth" is that female brains have larger corpus callosa than male brains.

I have to admit that I am not immune from gender bias.  When I first heard that women had larger corpus callosa than men, my immediate thoughts were towards how that could make sense.  I thought "ah, well then maybe that is why women are better at seeing the big picture or at multi-tasking" and other thoughts along those lines.  

What I definitely did NOT think was "I bet that was a small, poorly controlled study which did not even reach statistical significance."  Well as it turns out, I should have.  DeLacoste-Utamsing and Holloway (1982) analyzed only 14 brains (9 male and 5 female), and found that

"The average area of the posterior fifth of the corpus callosum was larger in females than in males (p=0.08)" DeLacoste-Utamsing and Holloway (1982) p. 1431

A result hardly worth speculating upon.

Leonard et al., 2008 also found some corpus callosum differences between the genders, but when they graphed the size of the corpus callosum against the size of the whole brain...

Figure 3B (female brains white circles, male brains filled squares)
They found a continuum. The difference in size between the female and male corpus callosum is entirely due to the difference in size of the female and male brain as a whole. 

As with Von Economo neurons, maybe brains of different sizes work similarly, but have to be shaped differently to do so.

So rather than wildly speculating that women are better at this or that because they have stronger connections between their hemispheres, we should put our efforts into discovering evolutionary reasons why small men would be better multi-taskers that large men.

© TheCellularScale
UPDATE (7/23/12): I just want to be perfectly clear. I don't actually think that small men think like women.  The whole point of this post is to show that popular studies explaining that 'men and women's brains are different' may sound like they make sense, but there is often another explanation. In this case: if you are going to claim that the size of the corpus callosum means that women are better multi-taskers, then you have to ALSO claim that small men are better multi-taskers. And that large women are worse multi-taskers.  (These seem like totally ridiculous claims to me, but feel free to construct an experiment to test these hypotheses). 

For more on gender and gender differences (or lack thereof) in the brain, see my previous posts:

ResearchBlogging.orgDeLacoste-Utamsing C, & Holloway RL (1982). Sexual dimorphism in the human corpus callosum. Science (New York, N.Y.), 216 (4553), 1431-2 PMID: 7089533

Leonard CM, Towler S, Welcome S, Halderman LK, Otto R, Eckert MA, & Chiarello C (2008). Size matters: cerebral volume influences sex differences in neuroanatomy. Cerebral cortex (New York, N.Y. : 1991), 18 (12), 2920-31 PMID: 18440950


  1. although i do have a gender bias i would like to know for what reason do they have this bigger portion and is there anything from growing up with certain lifestyles that wouold benefit this bigger growth

    1. This study is showing that the size of the corpus callosum is directly related to the size of the whole brain. Your question might as well be "why do women have smaller brains than men?" which is pretty easily explained by women having generally smaller bodies than men.

  2. That is a very interesting study because a lot of people are intrigued by the difference of men and women’s brain structure. You are right about it being a small study there should have been more people involved in this, so that the results could be more realizable. In my psychology class we learned we learned something similar so how the brains differ in men and women. The professor explained how women can let their minds think of nothing, while men are always thinking about something that will help them in no type of way, a waste of energy. Your blog is in the same spot because like you said women are better at multi-tasking than men. I definitely think that this article could have included more information, anyway, great job!

    1. I am not claiming that women are better multi-taskers than men. I was explaining my own bias when I learned about the corpus callosum myth. This bias was NOT based on evidence.
      Please read my post: Neurosexism and delusions of gender for more on gender differences (and lack thereof) in the brain. There is a link to it in the first sentence of the post.

  3. This post is super interesting!! Who knew that the size of the brain mattered more than the gender of the brain! This relates so much to my Psychology class because we are currently talking about different gender roles and what exactly defines 'gender'. When children grow up, they are raised based on their sex. They learn what is socially normal and not normal but is this accurate? If someone believes that they were born into the wrong sex, is it right for them to be criticized for going against 'the social norm' of that sex? Maybe their brain size has something to do with why certain people think the way they do! Smaller men think like bigger women?

  4. Amie C.-

    I think that transgenderism is usually viewed as a consequence of early hormone exposure+ experiences +V (where "V" is the vortex of other forces and circumstances we don't really know about yet.)

    The body size of transgendered folk does not seem to follow the established pattern of only small males becoming women, or large females becoming men. This is something which would correlate with brain size- but we don't actually know the brain size of the transgendered population, so we can't rule on the idea until that's measured.

    An interesting thought.

  5. Does anyone knows if the stereoptypical cognitive differences between men and women also are found to some degree in correlation to height? That would be interesting.

    Apparently "left-wing values" are more "feminine"; in a right-left wing politics scale, women on the right tend to be a little bit to the left of the men on the right, and women on the left, further to the left than men on the left. I wonder if leftists are usually shorter...